Long before any smokestack, this was a place of crossings. Puchuncaví marked one terminus of the Inca road system, the stone footpath that ran all the way to Cuzco, and a curaca, the empire's local representative, lived here to collect tribute and assert imperial authority over the region's peoples. When the Spanish arrived, the conquistador Pedro de Valdivia handed the valley to one of his soldiers, an Italian who happened to be a nephew of Pope Julius II. The land passed down through generations and was carved among heirs. A parish was founded in 1691. The villa was declared in 1875 and served at times as a provincial capital. After decades tethered administratively to neighboring Quintero, Puchuncaví finally won its own municipality on 13 September 1944, gathering its scatter of districts, La Greda, Las Ventanas, Los Maitenes, Campiche, Horcón, and the rest, under one name.

The industrial complex rose on the Quintero-Puchuncaví bay starting in the 1960s, and over the decades roughly fifteen polluting facilities clustered along the shore: a coal-fired power plant, an oil refinery, chemical terminals, and the Ventanas copper smelter. For the people who had lived here for generations, the cost was measured in their own bodies and their children's. In 2011 a cloud from the complex engulfed the school in La Greda; an estimated thirty-three children and nine teachers were sickened by the fumes. The worst came in August and September 2018, when more than three hundred people, many of them schoolchildren, fell ill after toxic substances drifted through the air, a yellowish haze that tests linked to chemicals including methyl chloroform, nitrobenzene, and toluene. These were not statistics to the families of Puchuncaví. They were sons and daughters sent home dizzy and vomiting, neighbors who wondered what they were breathing every day.

A 'sacrifice zone' is a place a society has decided, usually without asking the residents, to give up to pollution in exchange for cheaper power or industry somewhere else. Quintero and Puchuncaví became the most notorious example in Chile, the towns whose health was traded for the smelting of copper and the burning of coal. The people who lived there did not accept the bargain quietly. Fishermen, mothers, students, and environmental groups organized, protested, sued, and refused to disappear from the national conversation. Their persistence helped force a reckoning. In 2022 President Gabriel Boric announced that the state copper company would shut the Ventanas smelter, one of the area's worst polluters, and in May 2023 it ceased operations after roughly six decades. The closure did not undo the harm, but it was something the residents had fought for and won.

It would be wrong to leave Puchuncaví defined only by its smokestacks, because the coast itself is still beautiful and the life along it still real. North of the industrial bay the shoreline opens into beach towns like Maitencillo, with its Marbella resort, and the old fishing cove of Horcón, where boats still come in with the catch. Inland, communities like Campiche grow tomatoes and Pucalán works at coal and farming, much as their grandparents did. The town's population, just under thirteen thousand at the last detailed count, lives in the tension between the two Puchuncavís: the ancient place of fiestas and fishing, and the modern one that the rest of the country asked to bear a burden it did not choose. The people here carry both, and their fight to reclaim the first from the second is among the most important stories on this whole coast.